Flammable liquids such as gasoline, oil, and alcohol can be stored in floating roof tanks. Floating roof tanks are usually installed for environmental or economical reasons to limit product loss and reduce the emission of volatile organic compounds. Additionally, floating roof tanks sometimes are used to store flammable liquids because fumes of such materials can pose extreme risks of fire and/or explosion. Floating roof tanks therefore may be used to reduce the exposed surface area and reduce the vapor space of the flammable liquids, thereby reducing the risk of fires and/or explosions.
Lightning and/or other electrical discharges at or near the floating roof tanks, however, pose a serious risk of fire and/or explosion if the discharge ignites the fumes of the flammable liquids. This risk is particularly high at or near the rim of the floating roof of floating roof tanks, as an air gap typically exists between the floating roof and the shell of the floating roof tank. In fact, rim seal fires are the most common type of fire in floating roof tanks, particularly external floating roof tanks.
To mitigate the risk of rim seal fires, it is common to equip floating roof tanks with shunts around the rim of the floating roof. The shunts are spring loaded wiping contacts that engage the shell, thereby creating an electrical connection between the floating roof and the shell. The shell typically is connected to a grounding system, and therefore the floating roof can be grounded using shunts or other electrical connections between the floating roof and the shell. Thus, the threat of rim seal fires caused by electrical arcing or other electrical discharges between the floating roof and the shell can be reduced if the shunts and shells are maintained in working order.
The shunts, however, tend to wear out over time. Similarly, sludge and/or other materials can accumulate along the wall of the shell, preventing or degrading electrical connections between the shunts and the shell. As such, maintenance of floating roof tanks often includes inspection and/or repair of shunts, if the shunts are visible. Because shunts sometimes are submerged in the flammable liquids held by the floating roof tanks, such an inspection may be difficult if not impossible without first draining the floating roof tanks. Thus, data indicates that proper inspections of shunts and/or other floating roof tank structures may be properly performed as rarely as once every ten years. As such, these and other maintenance procedures may be inadequate for detecting degrading shunts and/or other structures, and therefore may fail to reduce the risk of rim seal fires.
It is with respect to these and other considerations that the disclosure made herein is presented.